The purpose of this proposed research is to purify and identify the principal mutagenic activity (Ames test) which forms in ground beef during frying under carefully controlled conditions using a custom-designed heating surface at 191 plus or minus 2 degrees C (a temperature commonly employed by major commercial hamburger restaurant franchises). We will investigate the potential carcinogenicity of the principal mutagenic component using histochemically-altered preneoplastic foci in rat liver as endpoint. Additionally, based on previous studies reported from this laboratory we will determine the role of proline in mutagen formation in ground beef during cooking.